您可以始终使用以下函数，以年和月为单位返回年龄（即1年4个月）

function getAge($dob, $age_at_date)
{  
    $d1 = new DateTime($dob);
    $d2 = new DateTime($age_at_date);
    $age = $d2->diff($d1);
    $years = $age->y;
    $months = $age->m;

    return $years.'.'.months;
}

或者如果希望在当前日期计算年龄，可以使用

function getAge($dob)
{  
    $d1 = new DateTime($dob);
    $d2 = new DateTime(date());
    $age = $d2->diff($d1);
    $years = $age->y;
    $months = $age->m;

    return $years.'.'.months;
}

您可以始终使用以下函数，以年和月为单位返回年龄（即1年4个月）

function getAge($dob, $age_at_date)
{  
    $d1 = new DateTime($dob);
    $d2 = new DateTime($age_at_date);
    $age = $d2->diff($d1);
    $years = $age->y;
    $months = $age->m;

    return $years.'.'.months;
}

或者如果希望在当前日期计算年龄，可以使用

function getAge($dob)
{  
    $d1 = new DateTime($dob);
    $d2 = new DateTime(date());
    $age = $d2->diff($d1);
    $years = $age->y;
    $months = $age->m;

    return $years.'.'.months;
}

最好的做法是使用PHP的DateTime（和DateInterval）对象。每个日期都封装在DateTime对象中，然后可以在两者之间进行区别：

$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");

DateTime对象将接受strtotime（）的任何格式。如果需要更具体的日期格式，则可以使用DateTime:：createFromFormat（）创建DateTime对象。

两个对象实例化后，使用DateTime:：diff（）从另一个对象中减去一个对象。

$difference = $first_date->diff($second_date);

$difference现在保存一个包含差异信息的DateInterval对象。var_dump（）如下所示：

object(DateInterval)
  public 'y' => int 0
  public 'm' => int 0
  public 'd' => int 20
  public 'h' => int 6
  public 'i' => int 56
  public 's' => int 30
  public 'invert' => int 0
  public 'days' => int 20

要格式化DateInterval对象，我们需要检查每个值，如果值为0，则将其排除：

/**
 * Format an interval to show all existing components.
 * If the interval doesn't have a time component (years, months, etc)
 * That component won't be displayed.
 *
 * @param DateInterval $interval The interval
 *
 * @return string Formatted interval string.
 */
function format_interval(DateInterval $interval) {
    $result = "";
    if ($interval->y) { $result .= $interval->format("%y years "); }
    if ($interval->m) { $result .= $interval->format("%m months "); }
    if ($interval->d) { $result .= $interval->format("%d days "); }
    if ($interval->h) { $result .= $interval->format("%h hours "); }
    if ($interval->i) { $result .= $interval->format("%i minutes "); }
    if ($interval->s) { $result .= $interval->format("%s seconds "); }

    return $result;
}

现在剩下的就是调用$differenceDateInterval对象上的函数：

echo format_interval($difference);

我们得到了正确的结果：

20天6小时56分30秒

用于实现目标的完整代码：

/**
 * Format an interval to show all existing components.
 * If the interval doesn't have a time component (years, months, etc)
 * That component won't be displayed.
 *
 * @param DateInterval $interval The interval
 *
 * @return string Formatted interval string.
 */
function format_interval(DateInterval $interval) {
    $result = "";
    if ($interval->y) { $result .= $interval->format("%y years "); }
    if ($interval->m) { $result .= $interval->format("%m months "); }
    if ($interval->d) { $result .= $interval->format("%d days "); }
    if ($interval->h) { $result .= $interval->format("%h hours "); }
    if ($interval->i) { $result .= $interval->format("%i minutes "); }
    if ($interval->s) { $result .= $interval->format("%s seconds "); }

    return $result;
}

$first_date = new DateTime("2012-11-30 17:03:30");
$second_date = new DateTime("2012-12-21 00:00:00");

$difference = $first_date->diff($second_date);

echo format_interval($difference);

我投票支持jurka的答案，因为这是我最喜欢的，但我有一个pre-php.5.3版本。。。

我发现自己在解决一个类似的问题——这就是我最初如何回答这个问题——但只是需要时间上的差异。但我的函数也很好地解决了这个问题，而且我自己的库中没有任何地方可以将它保存在不会丢失和遗忘的地方，所以……希望这对某人有用。

/**
 *
 * @param DateTime $oDate1
 * @param DateTime $oDate2
 * @return array 
 */
function date_diff_array(DateTime $oDate1, DateTime $oDate2) {
    $aIntervals = array(
        'year'   => 0,
        'month'  => 0,
        'week'   => 0,
        'day'    => 0,
        'hour'   => 0,
        'minute' => 0,
        'second' => 0,
    );

    foreach($aIntervals as $sInterval => &$iInterval) {
        while($oDate1 <= $oDate2){ 
            $oDate1->modify('+1 ' . $sInterval);
            if ($oDate1 > $oDate2) {
                $oDate1->modify('-1 ' . $sInterval);
                break;
            } else {
                $iInterval++;
            }
        }
    }

    return $aIntervals;
}

测试：

$oDate = new DateTime();
$oDate->modify('+111402189 seconds');
var_dump($oDate);
var_dump(date_diff_array(new DateTime(), $oDate));

结果是：

object(DateTime)[2]
  public 'date' => string '2014-04-29 18:52:51' (length=19)
  public 'timezone_type' => int 3
  public 'timezone' => string 'America/New_York' (length=16)

array
  'year'   => int 3
  'month'  => int 6
  'week'   => int 1
  'day'    => int 4
  'hour'   => int 9
  'minute' => int 3
  'second' => int 8

我从这里得到了最初的想法，我对其进行了修改以供使用（我希望我的修改也会显示在该页面上）。

通过从$aIntervals数组中删除不需要的间隔（例如“周”），或者添加$aExclude参数，或者在输出字符串时过滤掉它们，可以非常容易地删除它们。

这将尝试检测是否给定了时间戳，并将返回未来的日期/时间作为负值：

<?php

function time_diff($start, $end = NULL, $convert_to_timestamp = FALSE) {
  // If $convert_to_timestamp is not explicitly set to TRUE,
  // check to see if it was accidental:
  if ($convert_to_timestamp || !is_numeric($start)) {
    // If $convert_to_timestamp is TRUE, convert to timestamp:
    $timestamp_start = strtotime($start);
  }
  else {
    // Otherwise, leave it as a timestamp:
    $timestamp_start = $start;
  }
  // Same as above, but make sure $end has actually been overridden with a non-null,
  // non-empty, non-numeric value:
  if (!is_null($end) && (!empty($end) && !is_numeric($end))) {
    $timestamp_end = strtotime($end);
  }
  else {
    // If $end is NULL or empty and non-numeric value, assume the end time desired
    // is the current time (useful for age, etc):
    $timestamp_end = time();
  }
  // Regardless, set the start and end times to an integer:
  $start_time = (int) $timestamp_start;
  $end_time = (int) $timestamp_end;

  // Assign these values as the params for $then and $now:
  $start_time_var = 'start_time';
  $end_time_var = 'end_time';
  // Use this to determine if the output is positive (time passed) or negative (future):
  $pos_neg = 1;

  // If the end time is at a later time than the start time, do the opposite:
  if ($end_time <= $start_time) {
    $start_time_var = 'end_time';
    $end_time_var = 'start_time';
    $pos_neg = -1;
  }

  // Convert everything to the proper format, and do some math:
  $then = new DateTime(date('Y-m-d H:i:s', $$start_time_var));
  $now = new DateTime(date('Y-m-d H:i:s', $$end_time_var));

  $years_then = $then->format('Y');
  $years_now = $now->format('Y');
  $years = $years_now - $years_then;

  $months_then = $then->format('m');
  $months_now = $now->format('m');
  $months = $months_now - $months_then;

  $days_then = $then->format('d');
  $days_now = $now->format('d');
  $days = $days_now - $days_then;

  $hours_then = $then->format('H');
  $hours_now = $now->format('H');
  $hours = $hours_now - $hours_then;

  $minutes_then = $then->format('i');
  $minutes_now = $now->format('i');
  $minutes = $minutes_now - $minutes_then;

  $seconds_then = $then->format('s');
  $seconds_now = $now->format('s');
  $seconds = $seconds_now - $seconds_then;

  if ($seconds < 0) {
    $minutes -= 1;
    $seconds += 60;
  }
  if ($minutes < 0) {
    $hours -= 1;
    $minutes += 60;
  }
  if ($hours < 0) {
    $days -= 1;
    $hours += 24;
  }
  $months_last = $months_now - 1;
  if ($months_now == 1) {
    $years_now -= 1;
    $months_last = 12;
  }

  // "Thirty days hath September, April, June, and November" ;)
  if ($months_last == 9 || $months_last == 4 || $months_last == 6 || $months_last == 11) {
    $days_last_month = 30;
  }
  else if ($months_last == 2) {
    // Factor in leap years:
    if (($years_now % 4) == 0) {
      $days_last_month = 29;
    }
    else {
      $days_last_month = 28;
    }
  }
  else {
    $days_last_month = 31;
  }
  if ($days < 0) {
    $months -= 1;
    $days += $days_last_month;
  }
  if ($months < 0) {
    $years -= 1;
    $months += 12;
  }

  // Finally, multiply each value by either 1 (in which case it will stay the same),
  // or by -1 (in which case it will become negative, for future dates).
  // Note: 0 * 1 == 0 * -1 == 0
  $out = new stdClass;
  $out->years = (int) $years * $pos_neg;
  $out->months = (int) $months * $pos_neg;
  $out->days = (int) $days * $pos_neg;
  $out->hours = (int) $hours * $pos_neg;
  $out->minutes = (int) $minutes * $pos_neg;
  $out->seconds = (int) $seconds * $pos_neg;
  return $out;
}

示例用法：

<?php
  $birthday = 'June 2, 1971';
  $check_age_for_this_date = 'June 3, 1999 8:53pm';
  $age = time_diff($birthday, $check_age_for_this_date)->years;
  print $age;// 28

Or:

<?php
  $christmas_2020 = 'December 25, 2020';
  $countdown = time_diff($christmas_2020);
  print_r($countdown);

使用示例：

echo time_diff_string('2013-05-01 00:22:35', 'now');
echo time_diff_string('2013-05-01 00:22:35', 'now', true);

输出：

4 months ago
4 months, 2 weeks, 3 days, 1 hour, 49 minutes, 15 seconds ago

功能：

function time_diff_string($from, $to, $full = false) {
    $from = new DateTime($from);
    $to = new DateTime($to);
    $diff = $to->diff($from);

    $diff->w = floor($diff->d / 7);
    $diff->d -= $diff->w * 7;

    $string = array(
        'y' => 'year',
        'm' => 'month',
        'w' => 'week',
        'd' => 'day',
        'h' => 'hour',
        'i' => 'minute',
        's' => 'second',
    );
    foreach ($string as $k => &$v) {
        if ($diff->$k) {
            $v = $diff->$k . ' ' . $v . ($diff->$k > 1 ? 's' : '');
        } else {
            unset($string[$k]);
        }
    }

    if (!$full) $string = array_slice($string, 0, 1);
    return $string ? implode(', ', $string) . ' ago' : 'just now';
}